The present invention relates to methods of in vivo analysis and, in particular, to methods for determining the operability status of heart valves and the like. Heart valve prostheses have been used successfully since 1960. As stated by one author, the decade of 1960 will probably be remembered most in the annals of cardiology as the decade in which cardiac valve replacement became a reality. Of the nearly fifty different heart valves introduced over the last sixteen years, many have been discarded due to their lack of success. Of those remaining, several modifications have been made or are presently being made.
The most commonly used basic types of valves at present are the caged ball, the tilting disc, the caged disc, and tissue or porcine valves. A caged-ball-type valve is shown IN SITU within the blood stream in simplified form in operation in FIG. 1. A tilting-disc type is shown in similar manner in FIG. 2. At present, over ninety thousand prosthetic valves of different designs are used annually throughout the world.
Even after sixteen years of experience, the problems associated with heart-valve prostheses have not been totally eliminated. The most serious problems and complications associated with them are red-cell destruction, thrombosis formation, damage to the endothelial lining of the aortic walls, valve failure due to material fatigue or chemical change, leaks caused by failure of the valve to close properly, infection, and tearing of sewing sutures.
Because of the above mentioned problems, implanted prosthetic valves eventually show some degree of malfunction. If the malfunction of a prosthetic valve is not detected, it could be fatal to the patient. Except for a few valves of recent design, the moving parts of most prosthetic valves contain only plastic materials (specifically non-metallic) such that easily accomplished non-invasive testing cannot be done. Low intensity X-ray analysis through the injection of radiopaque dyes into the heart via catheterization is neither pleasant nor without certain dangers.
Wherefore, it is the object of the present invention to provide a simple non-invasive method of analysis of the operability of heart valves IN VIVO.